U.S. Pat. No. 3,256,355 relates to the dehydrogenation of ethylbenzene to make styrene. In said prior art, referring to the stream leaving the ethylbenzene dehydrogenation reactor, the latent heat of condensation of the contained steam is used to heat the reboilers of distillation columns in the overall process. Said stream is firstly washed with hot water to remove tars, then compressed and sent to the reboilers.
U.S. Pat. No. 4,288,234 describes an ethylbenzene dehydrogenation wherein the stream leaving the ethylbenzene dehydrogenation reactor is introduced in a cooling zone containing one or more cooling steps and a compression step. The remaining gases, essentially hydrogen, are washed with ethylbenzene and then polyethylbenzene to remove aromatics.
U.S. Pat. No. 4,628,136 describes an ethylbenzene dehydrogenation wherein the stream leaving the ethylbenzene dehydrogenation reactor is introduced in a conventional cooling zone where are recovered (i) a gaseous phase (essentially hydrogen), (ii) an organic phase (ethylbenzene and styrene) and (iii) an aqueous phase. Said aqueous phase is further mixed with fresh ethylbenzene then is vaporized while condensing the reflux of the ethylbenzene/styrene distillation column and then sent to the dehydrogenation catalyst.
U.S. Pat. No. 6,388,155 relates to a process for the production of styrene monomer from ethylbenzene comprising the steps of:
a) catalytically dehydrogenating said ethylbenzene in the presence of steam thereby catalytically producing a dehydrogenation effluent gas containing unreacted ethylbenzene and lighter components and styrene monomer and heavier components;
b) scrubbing said effluent gas with reflux to remove at least a portion of said styrene monomer and heavier components from said effluent gas;
c) condensing said scrubbed effluent gas thereby producing a liquid organic dehydrogenation mixture, an aqueous phase and a gaseous phase;
and
d) using a portion of said liquid organic dehydrogenation mixture as said reflux for said step b) of scrubbing.
In the bottoms of said scrubber of step b) an aqueous phase and an organic phase are recovered, said aqueous phase is mixed with aqueous phase recovered at step c) and said organic phase is fed to a distillation column for separation of the ethylbenzene and styrene monomer.
It has been discovered a new process wherein the dehydrogenation effluent of step a):
is quenched with an aqueous phase and
essentially all the steam present in the ethylbenzene dehydrogenation effluent stream is recovered in the bottom of the quench column.
One advantage is that most of the divinylbenzene and polymerics materials contained in said dehydrogenation effluent are easily removed. Said removal eliminates the fouling and plugging problems in condensers and other apparatus in the course of styrene recovering.
U.S. Pat. No. 3,515,764, GB 2 092 U.S. Pat. No. 3,515,764, 018, U.S. Pat. No. 3,515,765, U.S. Pat. No. 3,515,766 and U.S. Pat. No. 3,515,767 have described processes for recovering styrene in an ethylbenzene dehydrogenation effluent stream. In said prior arts the quenching apparatus has only an overhead effluent.